SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'df96acb4b76460b31d719c7b0fbbdf26acf24248e3934e8e6a2b6438acb7892c' 
  AND token = 'ERBTn9zERFiwZTItmXgvXMeYc7LDdIlXPCNwDBSusuo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}